You would want to write it like this:
myUITextObject.textAlignment = .center
(Edited to change from .Center to .center)
What you're looking for is the textAlignment property; try this:
myUITextObject.textAlignment = NSTextAlignmentCenter;
Another way to do it, is by using the storyboard.
In fact there is a Vertical and Horizontal Control that you can use for align your element inside the UITextField.In the case above that align the text to the top left:
Hope it helps,